Mendel Biotechnology Inc., 3935 Point Eden Way, Hayward, CA 94545, USA.
New Phytol. 2010 Jul;187(1):57-66. doi: 10.1111/j.1469-8137.2010.03251.x. Epub 2010 Apr 12.
CONSTANS is an evolutionarily-conserved central component of the genetic pathway that controls the onset of flowering in response to daylength. However, the specific biochemical mechanism by which the CONSTANS protein regulates the expression of its target genes remains largely unknown. *By using a combination of cell-based expression analysis and in vitro DNA binding studies, we have demonstrated that CONSTANS possesses transcriptional activation potential and is capable of directly binding to DNA. *CONSTANS was found to bind DNA via a unique sequence element containing a consensus TGTG(N2-3)ATG motif. This element is present in tandem within the FLOWERING LOCUS T promoter and is sufficient for CO binding and activity. The conserved CCT (CONSTANS, CONSTANS-like and TOC1) domain of CONSTANS was shown to be required for its recruitment to the DNA motif and other CCT-containing proteins were also found to have the ability to regulate gene expression via this element. *The CCAAT box, which has been previously hypothesized as a recruitment site for complexes containing the CONSTANS protein, potentiated CONSTANS-mediated activation but was not essential for CONSTANS recruitment to a target promoter or for its activity as a transcriptional factor.
CONSTANS 是控制植物开花时间的遗传途径中的一个进化保守的核心成分，它响应于日照长度。然而，CONSTANS 蛋白调节其靶基因表达的具体生化机制在很大程度上仍然未知。通过使用基于细胞的表达分析和体外 DNA 结合研究的组合，我们已经证明 CONSTANS 具有转录激活潜力，并且能够直接与 DNA 结合。发现 CONSTANS 通过含有共识 TGTG（N2-3）ATG 基序的独特序列元件结合 DNA。该元件在开花时间启动子中串联存在，并且足以结合 CO 和活性。CONSTANS 的保守 CCT（CONSTANS、CONSTANS-like 和 TOC1）结构域对于其募集到 DNA 基序是必需的，并且还发现其他含有 CCT 的蛋白质也具有通过该元件调节基因表达的能力。CCAAT 盒先前被假设为包含 CONSTANS 蛋白的复合物的募集位点，增强了 CONSTANS 介导的激活，但对于 CONSTANS 募集到靶启动子或作为转录因子的活性不是必需的。
